Akihiko Kubo

Sustainability analysis of rapid prototyping: material/resource and process perspectives

Sustainability of rapid prototyping (RP) depends on both model-building materials (wooden-materials, photo-resins, etc.) and model-building processes (additive processes – SLA, SLS, etc.; and subtractive processes – e.g., wood-sawing). In this study, a sustainability index is developed for RP processes, and this index incorporates such sustainability factors as volumetric quantity of model-building material, CO2 footprint and resource depletion of primary production of model-building material, energy consumption and CO2 emission of the model-building process. In addition, physical models have been created from the same 3D CAD data by using both SLA-based RP technology (additive process) and wooden-material-based RP technology (subtractive process). The subtractive process uses a specially designed CNC machine tool that removes the wooden-material using a circular-saw controlled by a 3D CAD model. The model-building process has been repeated for different scales of the same 3D CAD model. Using the experimental results, the sustainability index of the two RP technologies has been compared. The results help determine the critical size of a physical model of a given 3D CAD model and RP technology ensuring sustainability. In addition, the results show new avenues for improving the respective RP technologies in terms of sustainable manufacturing requirements.

On Some Eco-Indicators of Cutting Tools

This study deals with some eco-indicators of cutting tools. Eco-indicators of cutting tools are classified into three categories, namely, material-, process-, and geometry-related eco-indicators. Material-related eco-indicators consist of density, price, embodied energy, CO2 footprint, NOX, SOX, water usage, material processing energy, and recycle fraction of tool materials. Process-related eco-indicators consist of material removal rate, cutting velocity, feed rate, spindle speed, and surface coating. Geometry-related eco-indictors consist of special geometric features of cutting tool that make the tool’s performance robust in terms of process-related eco-indicators. The general definitions and representations of these indicators are described. Giving examples of cutting tools made of tungsten carbide and HSS, it is shown that further research is needed to develop an ideal cutting tool that is equally preferable in terms of material-, process-, and geometry-related eco-indicators.© 2011 ASME

Effect of cutting edge truncation on ductile-regime grinding of hard and brittle materials

Cutting edge truncation is a micro-truing process in which the diamond cutting edges of a grinding wheel are truncated and aligned at the same height. This process has been applied to the ultraprecision grinding of hard and brittle materials in order to improve the ground surface roughness. However, the theoretical investigation has not been clarified. In this study, computer simulation of surface plunge grinding has been performed. It is found that a surface roughness in the nanometer order can be generated by the truncation of a coarse-grained grinding wheel, but the contribution of such truncation to a decrease in the maximum grain depth of cut is insufficient. Thus, the proper selection of a fine-grained grinding wheel as well as suitable grinding conditions are necessary for ductile-regime grinding, which requires the maximum grain depth of cut to be less than a value realising ductile-mode material removal.

On the Surface Metrology of Bimetallic Components

A bimetallic component may perform better than its monometallic counterpart in terms of sustainability (i.e., cost, weight, and environmental impacts of primary material production). Thus, the usages of such components are likely to increase in the years to come. Three distinct segments (segments of the constituent materials and joint area) underlie a bimetallic component, necessitating a rather unique surface characterization methodology. The objective of this study is to shed some lights on the surface characterization of a bimetallic component using both conventional and non-conventional approaches. In order to get insights into the surface finish of a bimetallic component, specimens are prepared by joining bars made of commercially pure Titanium (Ti) and Aluminum (Al). The specimens are then turned under some predefined cutting conditions, and the surface profile heights across the joint area are measured by using noncontact surface metrology equipment. The surface profiles are characterized by using the conventional parameters. In addition, the complexity of the surfaces is quantified by using the information content based parameter. Moreover, to quantify the degree of uncertainty, probability/possibility distributions are induced from the profile heights. Both conventional and proposed parameters are equally important for quantifying the surface roughness of a bimetallic component.

Evaluation of Hard Materials Using Eco-Attributes

Hard materials based on Alumina (AN), Silicon Carbide (SC), Boron Carbide/Nitride (BC/N), Zirconia (ZN), and alike are often used to produce abrasive grains and coat cutting tools. These materials improve the performance of grinding/machining operations by providing an enhanced productivity, a longer grinder/tool life, and a better surface finish. On the other hand, they might leave some burdens on the environment. Therefore, eco-attributes (i.e., energy consumption, CO2 emission, NOX/SOX emission, water usage, recycle fraction, etc.) of these hard materials should be used to make an informed decision. This study deals with this issue and provides an evaluation of AN, SC, BC/N, and ZN based hard materials in terms of CO2 emission, NOX emission, SOX emission, and water usage. The outcomes of this study are useful for analyzing grinding and other abrasive processes for achieving eco-manufacturing.

Modeling and Simulation of 3D Surface Finish of Grinding

The main body of grinding knowledge comes from the experiments done by independent investigators. If such experimental results are not made both human- and machine-comprehensible from the very beginning, then it would be difficult to reuse the results using a computerized network or any other means. In this respect, intelligent systems are needed to create human- and machine-comprehensible models of important results like 3D surface finish, cutting force, tool wear, etc. From this perspective, this paper describes a method for modeling and simulation of 3D surface finish of grinding. A human-friendly simulation tool is developed to implement the method. The simulation result is compared with the real 3D surface finish and a close correlation is found. The presented model can be integrated with the collaborative machining networks for better utilization of grinding resources using computers (e.g., condition monitoring, process planning, automation) and even using humans (e.g., effective exchange of information among peers in the research community and in the industry).

Chip Formation Behaviour in Ultra-Precision Cutting of Electroless Nickel Plated Mold Substrates

Electroless nickel plating is used in mold manufacturing industries as a surface processing technology for providing hard, ductile, wear resistant and corrosion-resistant surfaces. In this work, we conducted single point diamond turning experiments on electroless nickel plated substrates at machining scales from the nanometric to the micrometer level, and the machining behaviour was investigated through examining the chip morphology and surface texture. Emphatically, the effect of cutting fluid was investigated in detail. The results showed that the chip formation mechanisms in dry cuts and wet cuts are significantly different. Dry cuts cause splitting, adhesion, folding and secondary deformation of the chips, leading to surface defects. The results indicated that an effective supply of cutting fluid to the cutting region is essentially important to achieve high quality surfaces.

A decision model for making decisions under epistemic uncertainty and its application to select materials

Abstract This study deals with both a decision model for making decisions under epistemic uncertainty and how to use it for selecting optimal materials under the same uncertainty. In particular, the proposed decision model employs a set of possibilistic objective functions defined by fuzzy numbers to handle a set of conflicting criteria. In addition, the model can calculate the compliance of a piece of decision-relevant (imprecise) information with a given objective function. Moreover, the model is capable to aggregate the calculated compliances for the sake of ranking a given set of alternatives against the set of conflicting criteria. The problem of selecting materials for making the body of a vehicle is considered as an example. In this problem, the indices for selecting the materials are unknown because the specifications regarding the vehicle body are not given. In addition, the data relevant to material properties entails a great deal of imprecision. The presented decision model can quantify the above-mentioned epistemic uncertainty in a lucid manner and generate a list of optimal materials.

Design for Manufacturing of IFS Fractals from the Perspective of Barnsley's Fern-leaf

ABSTRACTThis study deals with the design for manufacturing (DFM) of fractals created by a random walk called iterated function system (IFS). In particular, the DFM of an IFS-created fractal called Barnsleys fern-leaf is considered. The IFS dedicated for creating virtual models of a fern-leaf uses a set of four strictly-contracting affine mappings in the onto manner. The interactions among these mappings are studied in detail in order to identify some data structures. Based on the identified data structures, a DFM procedure is proposed. In the proposed DFM procedure, three out of the four mappings are employed in both the onto and one-to-one manner. The proposed DFM procedure is applied to the redesign of the shape (fern-leaf). Physical models of the redesigned fern-leaf are manufactured using both additive and subtractive manufacturing technologies (3-D printing and milling). The factors affecting accuracy of the physical models are also described. Although this study is limited to the shape of the fern-...

Elucidating Grinding Mechanism by Theoretical and Experimental Investigations

Grinding is one of the essential manufacturing processes for producing brittle or hard materials-based precision parts (e.g., optical lenses). In grinding, a grinding wheel removes the desired amount of material by passing the same area on the workpiece surface multiple times. How the topography of a workpiece surface evolves with these passes is thus an important research issue, which has not yet been addressed elaborately. The present paper tackles this issue from both the theoretical and the experimental points of view. In particular, this paper presents the results of experimental and theoretical investigations on the multi-pass surface grinding operations where the workpiece surface is made of glass and the grinding wheel consists of cBN abrasive grains. Both investigations confirm that a great deal of stochasticity is involved in the grinding mechanism, and the complexity of the workpiece surface gradually increases along with the number of passes.